Question

why do most people wear wrist watch on the left hand and very few only on right hand ?

Answer 1

Like many people have explained, wearing watches on the left (free) hand helps right-handed people maneuver their activities easier with their preferred hand. There's also another reason that I learned since I'm a leftie. Wearing watches, rings,... on your off-hand will prevent you from (i) injuring yourself with these accessories; (ii) damaging these accessories during your activities.

Answer 2

they can rotate the knob easily due to the dominant trait of right-handedness